Peppermint (Western Oregon) Nutrient Management Guide
Total Page：16
File Type：pdf, Size：1020Kb
NUTRIENT MANAGEMENT EM 9018-E December 2010 Peppermint (Western Oregon) J.M. Hart, D.M. Sullivan, M.E. Mellbye, A.G. Hulting, N.W. Christensen, and G.A. Gingrich he Pacific Northwest produces about 90 percent of the peppermint grown in the United States for oil, rootstock, and dried leaves. Dry peppermint leaves Tare used for tea and as a culinary herb. Peppermint oil is used to flavor chewing gum, toothpaste, mouthwashes, pharmaceuticals, and confectionary and aromatherapy products. Use for medicinal purposes is growing. Optimum oil quality and quantity are produced with ample daylight (usually more than 14 hours), warm day- time temperatures (85–95°F), and cool nighttime tempera- tures (55–60°F). Gale Gingrich, © Oregon State University Peppermint (Mentha piperita) is typically produced on deep, well-drained soil in locations with plentiful good- quality irrigation water. Historically, peppermint was Summary grown on soil series such as Chehalis, Cloquato, and New- berg. These deep, well-drained sandy loam and silt loam Lime Soil pH between 5.5 and 6.0 is “bottomland” soils were formed in mixed alluvium depos- adequate for peppermint produc- ited by the Willamette River and its tributaries. Currently, tion. Before planting, apply lime peppermint is also grown on well-drained silt loam valley according to Table 4 when the soil floor terrace soils, such as the Amity, Malabon, Willamette, pH is below 6.0. In established and Woodburn soil series. See the sidebar “Peppermint stands, apply lime when the soil pH production in the U.S.” (page 2) for more information. Peppermint reproduces vegetatively via “runners” is below 5.5. See pages 9–10. (rhizomes and stolons), which originate from the main Nitrogen (N) Application of no more than 200 to rootstock in early to mid-June (Figure 1, page 2). Stolons 250 lb N/a is necessary for pep- are stems growing at or just above the soil surface. Rhi- permint under good irrigation water zomes are stems growing at or just below the soil surface. management. Supply approximately Both have fewer leaves than do vertical stems and can 175 lb N/a before mid-May. Do not produce new roots and shoots from buds. Other crops with apply N after late July. Monitor soil stolons include bentgrass, strawberries, and some clovers. nitrate-N on a few typical fields to Kentucky bluegrass and creeping red fescue have rhi- evaluate trends in soil N availability zomes. New root growth from stolons and rhizomes near for the crop (June) and late-season the soil surface creates the impression that peppermint is soil nitrate-N accumulation (July a shallow-rooted crop. In fact, peppermint roots are easily and August). See pages 5–7. found 2 feet below the surface. Phosphorus (P) When soil test P is below 40 ppm, The “aggressive” or “invasive” reproductive nature apply P according to Table 5. of peppermint is exploited for establishment. Stands are See pages 10–11. established by planting stolons or rhizomes in rows. The Potassium (K) When soil test K is below 200 ppm, new plants spread quickly throughout the field; by the apply K according to Table 6. second year, rows are no longer distinguishable. Stands See page 11. Sulfur (S) Apply 20 to 30 lb S/a in early spring with the first application of N. J.M. Hart, Extension soil scientist; D.M. Sullivan, Extension soil scientist; M.E. Mellbye, area Extension agronomist; A.G. Hulting, Extension weed management specialist; N.W. Christensen, profes- 1 sor of soil science emeritus; and G.A. Gingrich, area Extension agronomist emeritus; all of Oregon State University. remain in production for as few as 3 or as many as 15 years. The average Willamette Valley peppermint field produces oil for 5 to 7 years. The oil is stored in glands on the leaves. As plants approach bloom, oil concentration increases, and the lower leaves drop from the plant. Oil concentration reaches its peak during bloom. Cutting is recommended at early bloom development stage to minimize leaf loss and maximize oil concentration and quality. Peppermint is a challenging crop to grow. Timely water and fertilizer applications are essential for optimum yields and quality oil. Nitrogen (N) is the most yield-limiting fertilizer nutrient. Liming to increase soil pH is necessary, Figure 1.—Peppermint is a perennial aromatic herb with erect, as is the addition of phosphorus (P), potassium (K), and square, branched stems. Leaves are arranged on the stem in opposite sulfur (S). pairs. Illustration: Kathy Merrifield This guide provides nutrient and lime recommendations for first-year and subsequent-year single-cut peppermint Double-cut peppermint crops in Clackamas, Benton, Lane, Linn, Marion, and Polk counties. For peppermint harvested twice in a grow- A few western Oregon peppermint fields are ing season, see the sidebar “Double-cut peppermint.” harvested twice in a growing season (June and Sep- The average peppermint oil yield in the Willamette tember). This practice is known as “double-cutting.” Valley is between 90 and 100 lb/a. Recommendations in Cutting twice in a season can increase oil yield by this guide are adequate to routinely produce a peppermint 30 to 40 percent, but oil quality will differ from that oil yield greater than 100 lb/a, assuming that disease-free of peppermint harvested during early bloom. For rootstock of an appropriate variety is planted on suitable information about oil quality, see the sidebar “Pep- soils free of verticillium wilt. permint oil quality” (page 8). Recommendations in this guide are based on research No research has been performed for double-cut conducted during the past 50 years on both large plots in peppermint in the Willamette Valley. Nitrogen rate is grower fields and small plots at Oregon State University likely to be the primary nutrient management adjust- research facilities in the Willamette Valley. See Appen- ment needed for this harvest system. At the first dix A (page 14) for a list of research projects. harvest (mid- to late June), 150 to 175 lb N/a has been accumulated by the crop. If the second harvest produces a similar hay yield, then two applications of 150 to 175 lb N/a will be needed. Peppermint production in the U.S. Peppermint production in the United States began acreage had increased to 15,900. Peppermint produc- in 1812, when stolons from England were planted in tion reached a peak of 50,000 acres in 1996. About Massachusetts. By 1835, production had moved to the half of Oregon’s mint production was in Marion, Linn, midwestern U.S. The soils and climate of Michigan and Lane, Benton, and Polk counties. Indiana were well suited to peppermint culture. These By 2008, harvested acreage in Oregon had states became the major peppermint-producing area by decreased to 21,000 acres. The Willamette Valley 1920, with production peaking in 1930. continues to grow approximately one-half of Oregon’s Verticillium wilt led to a decline in production in the peppermint crop. Peppermint is also produced in Midwest and an increase in acreage in Washington and Columbia County, in the irrigated areas of Morrow Oregon. After 1950, the Pacific Northwest became the and Umatilla counties, in the central Oregon counties largest peppermint- and spearmint-producing area in of Jefferson, Crook, and Deschutes, and in the Grande North America. Currently, the northwestern states of Ronde Valley of Union County. Montana, Idaho, California, Washington, and Oregon For Willamette Valley farms with irrigation, pep- produce between 85 and 90 percent of the peppermint permint oil is a high-value crop. During the peak years oil in the U.S. Oregon’s production is about one-third of of production, 25 to 40 percent of irrigated cropland in the national total. the Valley was planted to peppermint. Peppermint pest In Oregon, peppermint production began in 1908 near and weed control practices make it an ideal rotation Eugene. By 1939, 2,200 acres were harvested; by 1960, crop with grass seed, wheat, and sugar beets for seed. 2 Healthy plants with adequate root systems are required canadensis), and prickly lettuce (Lactuca serriola). See to obtain the greatest return from your fertilizer invest- Appendix C (page 16) for information about the influence ment. The nutrient recommendations in this guide assume of weeds on peppermint oil quality. Specific weed man- adequate control of weeds, insects, and diseases. Lack agement recommendations are found in the mint chapter of pest control cannot be overcome by the addition of of the PNW Weed Management Handbook and in OSU nutrients. Extension publication EM 8774, Weed Management in Common diseases of peppermint are verticillium wilt Mint. (Verticillium dahliae), powdery mildew (Erysiphe cicho- Numerous insects and invertebrate pests attack pepper- racearum), and leaf rust (Puccinia menthae). Planting mint, including the two-spotted spider mite (Tetranychus disease-free roots (certified wilt-free if possible) in fields urticae), root borers (Fumibotys fumalis), several cut- free of verticillium wilt helps assure a productive, healthy worms and armyworms, alfalfa looper (Autographa cali- stand for several years. See the sidebar “Variety and verti- fornica), cabbage looper (Trichoplusia ni), grasshoppers cillium wilt” for more information. (Camnula pellucida), multiple slug species, symphylans Nematodes are serious soil pests that can interact with (Scutigerella immaculata), and flea beetles Longitarsus( verticillium wilt to severely weaken mint stands. Sample waterhousei). For more information about insect manage- fields to assay nematodes and control